Is there a particular reason as to why English trainers prefer to teach Verb Tenses first over any other Grammar topic?

As a teacher, I first of all teach verbs to be and to do, then jump in to the tenses. Why, I think that is because the tenses form the pinnacle and foundation of any language, not just English. I mean, an absolute beginner wouldn't need to know how and when to use gerunds as his priority, but more importantly how to describe what he ate yesterday, or what he'll do when he goes home in the weekend.